Phenotypic Evaluation
To determine optimum PEG 6000 concentration for drought stress treatment, all the four soybean genotypes viz., DTP, DSP, DTL & DSL were subjected to different concentrations of PEG treatments viz., 10%,15% & 20% (w/v) in three biological replicates at germination stage, and the results revealed that 15% PEG is the optimum concentration for the evaluation of drought stress tolerance(Fig 1A). In the present study, GR and RL were used to evaluate drought tolerance of DTP, DSP, DTL & DSL genotypes under 15 % PEG and control conditions (Fig 1B & C) . The results revealed that all four genotypes showed normal germination under control conditions (Fig 1B ); however, under stress conditions tolerant genotypes viz., DTP & DTL showed normal germination (GR=100%) at the 4th day of stress treatment, whereas sensitive genotypes (DSP & DSL) revealed only 20% GR at the same time interval(Fig. 1C). Under control conditions, all genotypes showed normal RL, whereas the RL of all genotypes were reduced under stress relative to control condition (Fig. 1D ). Furthermore, the RL of sensitive genotypes (DSP & DSL) were significantly (P<0.01 ) reduced under stress compared to tolerant genotypes viz., DTP & DTS (Fig. 1D) , and transgression effect has been identified in DTL for RL. Hence, our results revealed that DTP and DTL are tolerant to drought stress, whereas DSP and DSL are drought-sensitive, and suggested that these contrasting genotypes can be effectively used for the analysis of drought tolerance.